Collaborative sensor coordination among the systems of a System of Systems (SOS) is currently being pursued by the Missile Defense Agency (MDA) to enhance both targeting and cueing accuracies in support of ballistic missile countermeasures or defense. The Navy is deploying its Cooperative Engagement Coordination (CEC) system which is intended to enable Aegis destroyers to pass tactical data among or between elements of the battle group. The MDA will require sensor coordination in order to provide effective and layered tactical and strategic missile defense in a missile defense System of Systems (SOS). Collaborative sensor coordination requires each element of a Missile Defense System to register its sensor(s) to local geodetic coordinate systems in order to minimize tracking and guidance errors, thereby reducing system handover and guidance errors between the target tracking and/or cueing systems and the interceptor(s). This “sensor registration” ultimately provides additional margin to the weapon system's pointing and divert error budgets, which in turn expands the battle space and enhances the overall warfare capability.
FIG. 1 illustrates a scenario 10 in which a first ship 1 and a second ship 2 lie at distances from a land mass 3. Item 6 represents the horizon. A communication satellite 4 is illustrated, and can communicate with both ships 1 and 2 by way of paths illustrated as “lightning bolts” 4a and 4b. Positional calibration measurements for ships 1 and 2 can be provided by global positioning system (GPS) signals 5s flowing from GPS satellites such as 5a and 5b, which follow various orbital paths, illustrated together as 5t. In the scenario 10 of FIG. 1, a hostile missile or target 12 is launched from a location 12s on land mass 3, and follows a path or trajectory 12t. In this scenario, defensive ship 2 is located closer to the missile launch site 12s than ship 1, and it acquires a sensor track earlier than ship 1. In this case, the sensor target track may use information from radar or infrared sensors. The target track information generated by ship 2 may be communicated to ship 1 by way of communications satellite 4, or it may be communicated by a direct path illustrated as 14. The sensors aboard ship 1 can fuse the data provided from the sensors aboard ship 1 with data from ship 2 to aid in acquiring its own track of the target missile 12. Ship 1 can then proceed to fire a weapon at the target missile 12. In the scenario 10 of FIG. 1, the weapon is an antimissile vehicle 16. Antimissile vehicle 16 follows a track 16t to intercept the target missile 12 at an intercept location 18.
Current technology in multisensor data fusion assumes that sensor and system bias registration techniques can be either (a) accounted for through covariance inflation techniques or (b) mitigated through use of ‘buffer states.’ The Cooperative Engagement Capability (CEC) System developed by Johns Hopkins University/Applied Physics Lab (JHU/APL), is an example of the covariance inflation technique. An example of the buffer state mitigation technique is described in U.S. Pat. No. 7,026,980 entitled MISSILE IDENTIFICATION AND TRACKING SYSTEM AND METHOD (MDOTS) and issued Apr. 11, 2006 in the name of Mavroudakis et al., This method uses the Unified Unbiased Rocket Equation Extended Kalman Algorithm (UUREEKA) described in U.S. patent application Ser. No. 10/972,943 entitled Computerized Method for Generating Low-Bias Estimates of Position of a Vehicle From Sensor Data, filed on Oct. 25, 2004 in the name of Boka et al. These techniques may under certain circumstances result in less-than-optimal fused track states attributable to sensor registration bias error.
The current art in sensor bias registration methods can be categorized into either real-time and non-real-time, and can alternatively be categorized as angular bias methods and positional bias methods. ARCHER, developed by Computer Science Corporation (CSC) and System Calibration Using Satellites (SCUS), developed by Lockheed Martin (LMCO), are examples of non-real-time method for angular registration bias estimation. Both of these methods make use of data in the form of satellite ephemeris to provide a reference which is used to estimate the angular bias error. SCUS and Instantaneous Sensor Alignment Auto-Calibration (ISAAC) described in U.S. patent application Ser. No. 11/149,692, filed Jun. 10, 2005 in the name of Boka et al are examples of angular bias registration methods. Sensor positional bias registration error amelioration or correction is described in U.S. patent application Ser. No. 11/504,561 and entitled “Method for Compensating for the Positional Errors of a Sensor,” (GPSLess) filed on or about Aug. 14, 2006 in the name of Mookerjee et al.
Improved or alternative sensor registration techniques and or methods are desired.